Solder ball attachment system

ABSTRACT

A solder ball attachment system for manufacturing an integrated circuit or the like is disclosed. The solder ball attachment system includes a flux station adapted to apply flux onto a substrate and a solder ball placement station adapted to place solder balls onto the flux. A conveyor assembly is included to move the substrate between the flux station and the solder ball placement station.

FIELD OF THE INVENTION

[0001] The present invention relates generally to packaging andmanufacturing of integrated circuits and the like, and more particularlyto a solder ball attachment system.

BACKGROUND INFORMATION

[0002] Integrated circuits in an electronic device are typicallyelectrically connected to multiple other integrated circuits orcomponents of the electronic device. For example, a processor chip in acomputer will be connected to one or more sources of power, to memorydevices or modules, input/output interfaces and the like. This canrequire that hundreds of electrical connections be made to the processorchip or integrated circuit (IC) chip. The IC chip will typically bemounted to a printed circuit board (PCB) and the multiple differentelectrical connections will need to be made between the IC chip and thePCB. One technology for making these multiple electrical connections isball grid array (BGA) technology. In BGA technology, sometimes hundredsof extremely small solder balls, on the order of a micron in diameter,must be precisely placed according to a predetermined pattern to makeelectrical contact between conductive pins or pads on the IC chip andconductive pads on the substrate of the PCB. A misplacement of fewmicrons or less can result in a defective product.

[0003] The predetermined pattern in which the solder balls are placedwill vary from one particular IC chip design to another. When a new ICchip is under development, the process for attaching or placing thesolder balls must be confirmed or certified as being accurate andreliable before being implemented in a high volume manufacturingoperation. A manual ball attachment jig is typically used in thedevelopment stage but this arrangement and process is time consuming andcostly to load and place the balls and can delay the certification oracceptance of a new product and the process for manufacturing theproduct.

[0004] Accordingly, for the reason stated above, and for other reasonsthat will become apparent upon reading and understanding the presentspecification, there is a need for a semiautomatic solder ballattachment system that is efficient to shorten the lead time ofdevelopment activities and reduce costs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a perspective view of a solder ball attachment system inaccordance with the present invention.

[0006]FIG. 2 is a detailed perspective view of a flux station for theball attachment system of FIG. 1.

[0007]FIG. 3 is a detailed perspective view of a tray portion of a ballplacement station for the ball attachment system of FIG. 1.

[0008]FIG. 4 is a detailed side elevation view of a pivotable carriageassembly of a ball placement station in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings which form apart hereof, and in which is shown by way of illustration specificembodiments in which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the present invention.

[0010]FIG. 1 shows a perspective view of a solder ball attachment system100 in accordance with the present invention. The solder ball attachmentsystem 100 includes a flux station 102 to apply flux to a substrate 104and a solder ball placement station 106 to place solder balls onto thesubstrate 104. The flux station 102 and the solder ball placementstation 106 are mounted on a platform 108 adjacent one another. Aconveyor assembly 110 is also mounted on the platform 108 and moves thesubstrate 104 between the flux station 102 and the solder ball placementstation 106. The conveyor assembly 110 includes a belt or pair ofconveyor belts 112. The belts 112 is driven by a motor 114 and a handcrank 116 may be provided to operate the conveyor belts 112 manually. Asubstrate holder or support 118 rests on or is attachable to theconveyor belts 112 to hold the substrate 104 during processing.

[0011] The solder ball attachment system 100 further includes analignment arrangement 119 for proper alignment of the substrate 104during processing in the flux station 102 and the solder ball placementstation 106. As part of the alignment arrangement 119, the substratesupport 118 may include a plurality guide pins 120 mounted thereon forproper alignment of the substrate 104 during processing in the fluxstation 102 and solder ball placement station 106.

[0012] To begin a solder ball placement process, the substrate 104 isplaced onto the substrate support 118 on the conveyor belt or belts 112and the substrate 104 is moved into proper position at the flux station102. Referring also to FIG. 2 which is a detailed perspective view ofthe flux station 102, the flux station 102 includes a flux screen 122.The flux screen 122 is lowered over the substrate 104. The flux screen122 has at least two guide holes 124 formed therein through which theguide pins 120 of the substrate support 118 are inserted for alignmentof the flux screen 122 with the substrate 104. The flux screen 122 has aplurality of openings 126 formed therein in a predetermined patternthrough which flux is applied or printed onto the substrate 104according to the predetermined pattern. The predetermined pattern of theopenings 126 may vary according to the design of the particular IC chipand the required placement of the solder balls on the substrate 104 tomake electrical connections between the particular IC chip andconductive pads 128 (FIG. 1) formed on the substrate 104.

[0013] The alignment arrangement 119 may also include a plurality ofadjustment screws 130 selectively positioned around a perimeter or sides132 of the flux station 102 to precisely adjust the placement of theopenings 126 in the flux screen 122 relative to the conductive pads 128formed on the substrate 104 for proper alignment between the opens 126and the conductive pads 128. After alignment, the flux screen 122 maythen be clamped in place by clamp screws 134 to prevent the flux screen122 from moving relative to the substrate 104 during application of theflux.

[0014] The flux station 102 also includes a flux applicator assembly136. The flux applicator assembly 136 includes a first upright supportmember 138 attached to one side 140 of the flux station 102 and a secondupright member 142 attached to another side 144 of the flux station 102opposite to the one side 140. A horizontal support member 146 issuspended between the first and second upright support members 138 and140 at a predetermined distance above the flux screen 122. Thehorizontal support member 146 is preferably hinged to the first uprightmember 138 by a hinge arrangement 148 and the horizontal support member146 may be attached to the second upright support member 142 by aremovable pin 150 or the like. This horizontal support member 146 canthen be swung open to remove or replace the flux screen 122. Thehorizontal support member 146 has a longitudinal slot 152 formed thereinthrough which a handle 154 is attached to a squeeze blade 156. Thesqueeze blade 156 may be made from a resilient material such a flexibleplastic or rubber type material with one end 158 in sliding contact withthe upper or exposed surface of the flux screen 122. The handle 154 isslidable within the slot 152 to move the squeeze blade 156 back andforth across the flux screen 122 to push or force flux uniformly throughthe openings 126 and onto the substrate 104. The flux will then beapplied or printed evenly or uniformly on the substrate 104 in thepredetermined pattern.

[0015] After flux is applied to the substrate 104, the flux screen 122is removed from the substrate 104 and the conveyor belts 112 may beactivated to move the substrate 104 to the solder ball placement station106. A conveyor belt operation switch 160 (FIG. 1) is mounted to theplatform 108 and is electrically connected to the motor 114 to controlthe operation of the motor 114 to move the conveyor belts 112 in aforward direction or a reverse direction. In one position the conveyorswitch 160 causes the motor 112 to move the substrate holder 118 fromthe flux station 102 to the ball placement station 106 and in anotherswitch position, the conveyor operation switch 160 causes the substrateholder 118 to move in an opposite direction.

[0016] Referring also to FIG. 3 which is a detailed perspective view ofa tray portion 162 of the solder ball placement station 106, the trayportion 162 includes a first section or ball placement section 164 and asecond section or ball bin 166. A ball placement mask 168 is mounted inthe first section 164 and the second section or ball bin 166 is wherethe solder balls 169 are stored. The ball placement mask 168 is mountedto an underside of the first section 164 by an attachment mechanism 170.The attachment mechanism 170 may be a latch-arrangement or magneticholders. The ball placement mask 168 is properly aligned to the firstsection 164 by guide holes 171 formed in the ball placement mask 168which are received on guide pins 172 formed on the underside of thefirst section 164.

[0017] Each section 164 and 166 has a respective ramp 173 and 174 thatslopes away from a center segment 175 of the tray portion 162.Accordingly, the solder balls 169 will be retained in the ball bin 166when the tray portion 162 is level in a non-ball placement ornon-operational position.

[0018] Referring also to FIG. 4 which is a detailed view of a portion ofa pivotable carriage assembly 176 of the solder ball placement station106. The pivotable carriage assembly 176 includes a lower portion orsubstrate support holder 177 and an upper portion or tray portionsupport 178. As the conveyor belts 112 move the substrate support 118into the solder ball placement station 106, side edges 179 of thesubstrate support 118 will be received into recesses 180 formed in thesubstrate support holder 177 of the pivotable carriage assembly 176.When the substrate support 118 is in proper position at the solder ballplacement station 106, an “UP” illuminated pushbutton 181 (FIG. 1) willturn on. The “UP” pushbutton 181 may then be pushed to operate a pair ofactuators 182 to raise the substrate support holder 177 and substrate104 to position the substrate 104 under the ball placement mask 168. Theactuators 182 are each respectively mounted proximate to opposite endsof the tray portion holder 178 of the pivotable carriage assembly 176,as best shown in FIG. 1. Each of the actuators 182 may be an aircylinder or similar device to raise the substrate support holder 177into position and to lower the substrate support holder 177 andsubstrate 104 after a ball placement operation.

[0019] The tray portion 162 is mounted to the tray portion holder 178.The tray portion holder 178 has a plurality of guide posts 183 formed onan underside 184 thereof. As the substrate support holder 177 is raised,the guide posts 183 will be received into respective guide holes 185formed in the substrate support holder 177 to properly align thesubstrate support 118 and substrate 104 with the ball placement mask168. Additionally, a pair of stability shafts 186 are mounted to thesubstrate support holder 177 at each end thereof proximate to eachactuator 182, as best shown in FIG. 1. The stability shafts 186 eachextend through openings 187 formed in the tray portion holder 178 andguide movement of the substrate support holder 177 into proper positionwith the tray portion holder 178 and the substrate 104 into properalignment with the ball placement mask 168 for a ball placementoperation.

[0020] Referring also back to FIG. 1, the tray portion 162 of the solderball placement station 106 is mounted in the tray portion holder 178 ofthe pivotable carriage assembly 176. The pivotable carriage assembly 176is pivotably mounted at two opposite ends thereof to a pair ofrespective stanchion members 189. The stanchion members 189 are mountedon the platform 108 and support the pivotable carriage assembly 176 overthe conveyor assembly 110 at the solder ball placement station 106. Thepivotable carriage assembly 176 is retained in a level position whilethe substrate support 118 is raised to a location under the tray portion162. After alignment of the substrate support 118 with the tray portion162, the pivotable carriage assembly 176 is released and may be pivotedto a position to cause the solder balls 169 (FIG. 3) to roll from theball bin section 166 into the first section 164 of the tray portion 162containing the ball placement mask 168 (FIG. 3). The ball placement mask168 has a plurality of holes 190 formed therein in a selected pattern toplace the solder balls 169 on the substrate 104 according to theselected pattern. The selected pattern of holes 190 may be substantiallythe same as or coordinate with the predetermined pattern of openings 126(FIG. 2) formed in the flux screen 122 for applying the flux. When thesolder balls 169 roll over the ball placement mask 168, the solder balls169 will drop by gravity into any unfilled holes 190 in the mask 168 andare placed or attached to the substrate 104 according to the selectedpattern of holes 190. The pivotable carriage assembly 176 may be tiltedback and forth until all of the holes 190 have been filled with a solderball 169. The carriage assembly 176 is then tilted or pivoted to aposition to cause all remaining or unused solder balls 169 to roll backinto the ball bin 166 where the balls 169 are retained until the nextsubstrate 104 is received for processing. The carriage assembly 176 maybe tilted or pivoted by a wheel 191 attached to an axle (not shown) ofthe carriage assembly 176 through a hub of the stanchion 189.

[0021] After placement of the solder balls 169 on the substrate 104, thecarriage assembly 176 is returned and retained in a level or horizontalposition. A “DOWN” illuminated pushbutton 192 is turned on. The “DOWN”pushbutton 192 is pushed to operate the actuators 182 to lower thesubstrate support 118 back onto the conveyor belts 112. The conveyorbelt operation switch 160 may then be operated in the reverse directionto move the substrate support 118 from the solder ball placement station106. The completed substrate 104 may be removed from the substratesupport 118 and another unfinished substrate may be placed on thesupport 118 for solder ball placement.

[0022] The solder ball attachment system 100 also preferably includes apower ON/OFF switch 194 mounted on the platform 108 to control theoverall application of power to the solder ball attachment system 100.The solder ball attachment system 100 may also include actuator covers196 to cover the actuators 182 and protect them from damage.

[0023] Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiment shown. This application isintended to cover any adaptations or variations of the presentinvention. Therefore, it is intended that this invention be limited onlyby the claims and the equivalents thereof.

What is claimed is:
 1. A solder ball attachment system, comprising: aflux station adapted to apply flux onto a substrate; a solder ballplacement station adapted to place solder balls onto the substrate; anda conveyor assembly adapted to move the substrate between the fluxstation and the solder ball placement station.
 2. The solder ballattachment system of claim 1, wherein the flux station comprises a fluxscreen having a plurality of openings formed therein in a predeterminedpattern to apply flux onto the substrate according to the predeterminedpattern.
 3. The solder ball attachment system of claim 1, wherein theflux station comprises a flux screen adapted to print flux material ontothe substrate.
 4. The solder ball attachment system of claim 1, whereinthe flux station includes an applicator assembly adapted to apply fluxto the substrate.
 5. The solder ball attachment system of claim 1,wherein the solder ball placement station comprises a solder ballplacement mask having a plurality of holes formed therein in a selectedpattern to place the solder balls on the substrate according to theselected pattern.
 6. The solder ball attachment system of claim 5,further comprising at least one actuator adapted to position thesubstrate relative to the solder ball placement mask for properplacement of the solder balls.
 7. The solder ball attachment system ofclaim 6, further comprising a substrate support adapted to hold thesubstrate during processing and wherein the at least one actuator is anair cylinder that raises the substrate support beneath the solder ballplacement mask.
 8. The solder ball attachment system of claim 1, furthercomprising an indicator adapted to identify when the substrate isproperly positioned relative to the solder ball placement station. 9.The solder ball attachment system of claim 8, wherein the indicator isone of a stop and an indicator light.
 10. The solder ball attachmentsystem of claim 8, further comprising: a solder ball placement maskadapted to place the solder balls according to a selected pattern ofholes formed in the solder ball placement mask; and at least oneactuator adapted to position the substrate relative to the solder ballplacement mask for proper placement of the solder balls and wherein theindicator is a light and a pushbutton to operate the at least oneactuator.
 11. The solder ball attachment system of claim 1, furthercomprising a substrate support attachable to the conveyor assembly tohold the substrate during processing.
 12. The solder ball attachmentsystem of claim 1, wherein the solder ball placement station comprises:a pivotable carriage assembly; a solder ball placement mask having aplurality of placement holes formed therein in a predetermined pattern,the solder ball placement mask being mounted in the pivotable carriageassembly to cause solder balls to roll about on the solder ballplacement mask and to drop into each of the plurality of placement holeswhen the carriage assembly is pivoted.
 13. The solder ball attachmentsystem of claim 12, wherein the solder ball placement station comprisesa solder ball bin for storage of solder balls, wherein at least aportion of the solder balls are released from the bin when the carriageassembly is pivoted and any solder balls that do not fill one of theplurality of placement holes are returned to the bin.
 14. A solder ballattachment system, comprising: a flux station including a flux screenhaving a plurality of openings formed therein in a predetermined patternadapted to apply flux onto a substrate according to the predeterminedpattern; a solder ball placement station including a solder ballplacement mask having a plurality of placement holes formed therein in aselected pattern to place solder balls on the flux according to theselected pattern; and a conveyor assembly adapted to move the substratebetween the flux station and the solder ball placement station.
 15. Thesolder ball attachment system of claim 14, wherein the flux stationcomprises an applicator assembly adapted to apply flux to the substrate.16. The solder ball attachment system of claim 14, wherein theapplicator assembly comprises a squeeze blade.
 17. The solder ballattachment system of claim 14, wherein the flux station further includesan alignment arrangement adapted to properly align the flux screen withthe substrate.
 18. The solder ball attachment system of claim 17,wherein the alignment arrangement comprises a plurality of adjustmentscrews selectively positioned around a perimeter of the flux station toadjust the positioning of the flux screen relative to the substrate. 19.The solder ball attachment system of claim 17, wherein the alignmentarrangement comprises a plurality of guides adapted to properly positionthe flux screen relative to the substrate.
 20. The solder ballattachment system of claim 14, wherein the solder ball placement stationcomprises a pivotable carriage assembly adapted to cause solder balls toroll about on the solder ball placement mask and to drop into one of theplurality of placement holes when the carriage assembly is pivoted. 21.The solder ball attachment system of claim 20, wherein the solder ballplacement station comprises a solder ball bin for storage of solderballs, wherein at least a portion of the solder balls are released fromthe bin when the carriage assembly is pivoted and any solder balls thatdo not fill one of the plurality of placement holes is moved back intothe bin.
 22. The solder ball attachment system of claim 14, wherein thepredetermined pattern and the selected pattern are coordinated.
 23. Amethod for placing solder balls on a substrate, comprising: applyingflux to the substrate according to a predetermined pattern at a fluxstation; conveying the substrate from the flux station to a solder ballplacement station; and depositing solder balls on the flux according toa selected pattern at the solder ball placement station.
 24. The methodof claim 23, wherein applying the flux to the substrate comprises:aligning a flux screen over the substrate; and forcing the flux througha plurality of opening formed in the flux screen in the predeterminedpattern.
 25. The method of claim 23, wherein depositing solder balls onthe flux comprises: aligning the substrate with a solder ball placementmask; and causing a plurality of solder balls to each drop into one of aplurality of holes formed in the solder ball placement mask.
 26. Themethod of claim 25, wherein the solder ball placement mask is mounted ina carriage assembly and wherein depositing solder balls on the fluxcomprises pivoting the carriage assembly to cause the plurality ofsolder balls to each drop into one of the plurality of holes.
 27. Themethod of claim 23, further comprising returning any solder balls notdeposited on the flux to a ball bin.